Olefins from paraffins and carbonyl sulfide



United States Patent 3,429,943 OLEFINS FROM PARAFFINS AND CARBONYL SULFIDE Alvin E. Trevillyan, Glenwood, and Robert A. Sanford,

Homewood, Ill., assignors to Sinclair Research, Inc.,

New York, N.Y., a corporation of Delaware N0 Drawing. Filed Apr. 19, 1967, Ser. No. 631,856 U.S. Cl. 260-6333 5 Claims Int. Cl. C07c 5/18 ABSTRACT OF THE DISCLOSURE Parafiinic hydrocarbons are converted to olefins by reacting the paraffin with carbonyl sulfide in the absence of molecular oxygen and at a temperature of from about 1000 to 1300" F. Olefins are obtained selectively and may be separated from other products by conventional means.

This invention relates to an improved process for the preparation of olefins from paraflins. More particularly, this invention concerns the use of carbonyl sulfide in converting paraffins to olefins.

Previous work in employing sulfur in the dehydrogenation of paraflins to produce olefins and/ or diolefins has frequently led to a variety of products and tars. By the process of the present invention, high selectivity to olefins is achieved with a minimum of side products by reacting parafiins with carbonyl sulfide at elevated temperatures.

In accordance with the process of the present invention, the parafiin is dehydrogenated in the vapor phase, in the absence of molecular oxygen and at an elevated temperature of about 1000 to 1300 F., preferably about 1100 to 1300 F. Such temperatures may be employed only to initiate the reaction, and the temperature may be decreased after initiation of the reaction to temperatures as low as about 400 F. to complete the reaction. When reaction temperatures lower than these are employed, there may be a loss of selectivity to olefins and other compounds maybe formed instead.

From about 0.5 to 10 moles, preferably about 1 to 5 moles, of parafiin may be used per mole of carbonyl sulfide in the reaction mixture of this invention. The residence times for the dehydrogenation process may vary, e.g., from about 0.1 to 5 minutes, and may often be from about 0.4 to 3 minutes. If desired, an inert diluent or vacuum can be employed to reduce the hydrocarbon partial pressure of the hydrocarbon feed. Various essentially inert gaseous diluents can be employed but it is preferred to use nitrogen, hydrogen, or methane. The inert gas is usually present in an amount of about 0.5 to 50 moles, preferably about 5 to 25 moles, per mole of hydrocarbon feed. Although the reaction may be effected at substantially elevated total pressures, such are not preferred.

An olefin product is obtained selectively in the process of the invention, and the olefin may be separated using conventional procedures, from the other products which are formed, such as CO and H S. Advantageously the CO may be used to prepare additional carbonyl sulfide.

The hydrocarbon feeds of the present invention are dehydrogenatable paraflins, including cycloparaflins and aromatic-substituted parafiins, especially of 2 to about 16 carbon atoms. Typical paraffins include ethane, propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, neohexane, cyclohexane, ethylcyclohexane, decane, pentadecane, ethylbenzene, etc. The preferred feeds are the normal and branched chain paratfins, including the cyclic parafiins such as cyclopentane and cyclohexane. Suitable aromatic-substituted paraflins include aromatic feeds containing at least one lower alkyl group of say about 2 to 4 carbon atoms, as in the case of ethylbenzene. Whether the principal reaction occurring is a straight dehydrogenation as opposed to dehydrocyclization, will be dependent in large part upon the feeds selected. Both dehydrogenation to create one or two bond-containing products and dehydrocyclization may occur with some feeds. Particularly high selectivities to desired product are usually obtained With the branched chain feeds of at least 4 carbon atoms, usually up to 12 carbon atoms, which contain a neo or quaternary carbon atom.

The following example is included to further illustrate the present invention but is not to be considered limiting.

EXAMPLE I Examples I to IV in Table I illustrate the application of the present invention. These examples were carried out by passing a mixture of carbonyl sulfide and isobutane into a stainless steel reactor having a void volume of 54 cc. The reactor effiuent was passed directly into a sampling valve and analyzed by gas chromatography. The reaction conditions and the results of these examples are Table I shows the selectivity to isobutylene and the percentage of COS reacting at varying temperatures and the residence times.

What is claimed is:

1. A process for the preparation of olefin which comprises contacting in the vapor phase and in the absence of molecular oxygen, parafiin containing from 2 to about 16 carbon atoms with carbonyl sulfide at temperatures of about 1000 to 1300 F. to form olefin.

2. The process of claim 1 wherein the mole ratio of parafiin to carbonyl sulfide is about 0.5 to 10:1.

3. The process of claim 1 wherein the reaction temperature is about 1100 to 1300 F., the residence time is about 0.4 to 3 minutes, and the mole ratio of paraffin to carbonyl sulfide is about 1 to 5:1.

4. The process of claim 3 wherein the parafiin is isobutane.

5. The process of claim 2 wherein the parafiin is isobutane.

References Cited UNITED STATES PATENTS 3,230,l61 l/l966 Gunning 204-162 DELBERT E. GANTZ, Primary Examiner.

G. E. SCHMITKONS, Assistant Examiner. 

